Simplify the following Boolean expressions, using four$-$variable K$-$maps:

$($a$)AB{C}^{\text{'}}{D}^{\text{'}}+A{B}^{\text{'}}C+B^{\text{'}}{C}^{\text{'}}{D}^{\text{'}}+A{B}^{\text{'}}CD+B^{\text{'}}{C}^{\text{'}}D$

$($b$)*w^{\text{'}}{x}^{\text{'}}{y}^{\text{'}}+w^{\text{'}}{x}^{\text{'}}yz+x^{\text{'}}{y}^{\text{'}}z+xyz+y^{\text{'}}{z}^{\text{'}}$

$($c$)A^{\text{'}}{B}^{\text{'}}CD+A^{\text{'}}BC+C^{\text{'}}D+$ABCD$+A{B}^{\text{'}}C$

$($d$)A^{\text{'}}{B}^{\text{'}}{C}^{\text{'}}+A^{\text{'}}BD+A^{\text{'}}B{C}^{\text{'}}{D}^{\text{'}}+B{C}^{\text{'}}D+$ABCD